Greenbusch Memorandum Template

p) 206.378.0569 f) 206.378-0641 www.greenbusch.com 1900 West Nickerson Street, Suite 201 Seattle, WA 98119

DATE: August 15, 2019

TO: Lee Momon – Seattle Public Utilities

FROM: Ellie Myers– The Greenbusch Group, Inc. Justin Morgan, INCE– The Greenbusch Group, Inc. RE: North Transfer Station –2019 Q3 Noise Monitoring Report

Transmitted by: Mail Delivery Fax E-mail

INTRODUCTION

The intent of this memorandum is to present the results of staffed sound level measurements conducted on July 6, 2019 and July 10, 2019 to document daytime and nighttime sound levels from operations at the North Transfer Station and to determine compliance with applicable regulatory criteria.

NOMENCLATURE

The auditory response to sound is a complex process that occurs over a wide range of frequencies and intensities. Decibel levels, or “dB,” are a form of shorthand that compresses this broad range of intensities with a convenient numerical scale. The decibel scale is logarithmic. For example, using the decibel scale, a doubling or halving of energy causes the sound level to change by 3 dB; it does not double or halve the sound loudness as might be expected.

The minimum sound level variation perceptible to a human observer is generally around 3 dB. A 5-dB change is clearly perceptible, and an 8 to 10 dB change is associated with a perceived doubling or halving of loudness. The human ear has a unique response to sound pressure. It is less sensitive to those sounds falling outside the speech frequency range. Sound level meters and monitors utilize a filtering system to approximate human perception of sound. Measurements made utilizing this filtering system are referred to as “A weighted” and are called “dBA”.

Common sound pressure levels are presented in Table 1.

August 15, 2019 Page 2 North Transfer Station – Third Quarter 2019 Noise Monitoring Report

The Greenbusch Group, Inc. p) 206.378.0569 f) 206.378-0641 www.greenbusch.com 1900 West Nickerson Street, Suite 201 Seattle, WA 98119

Table 1. A-weighted Levels of Common Sounds

Sound Sound Level (dBA)

Approximate Relative

Loudness1

Jet Plane @ 100 feet 130 128

Rock Music with Amplifier 120 64

Thunder, Danger of Permanent Hearing Loss

110 32

Power Mower 100 16

Food Blender at 3 feet 90 8

Busy Street 80 4

Interior of Department Store 70 2

Ordinary Conversation at 3 feet 60 1

Quiet Car at Low Speed 50 1/2

Average Office 40 1/4

City Residence, Interior 30 1/8

Quiet Country Residence, Interior 20 1/16

Rustle of Leaves 10 1/32

Threshold of Hearing 0 1/64

1. As compared to ordinary conversation at 3 feet.

Source: US Department of Housing and Urban Development, Aircraft Noise Impact Planning Guidelines for Local Agencies, November 1972., California Department of Transportation

Metrics

• Equivalent Sound Level, Leq Leq is the A-weighted level of a constant sound having the same energy content as the actual time-varying level during a specified interval. The Leq is used to characterize complex, fluctuating sound levels with a single number. Typical intervals for Leq are hourly, daily and annually.

• Maximum Sound Level, Lmax Lmax is the maximum recorded root mean square (rms) A-weighted sound level for a given time interval or event. Lmax “fast” is defined as a 125-millisecond time-weighted maximum, while Lmax “slow” corresponds to a 1-second time-weighted maximum. All values in this report are “fast” time-weight, which corresponds closest to the typical response time of the human ear.

• Sound Pressure Level, SPL Sound pressure level correlates with what is heard by the human ear. SPL is defined as the squared ratio of the sound pressure with reference to 20 μPa. Sound pressure is affected by distance, path, barriers, directivity, etc.



REGULATORY CRITERIA

The Seattle Municipal Code (SMC) Section 25.08 specifies permissible sound levels within the City of Seattle. SMC 25.08.410 defines allowable exterior sound level limits based on land use zoning, as listed in Table 2 below.

Table 2. Exterior Sound Level Limits, Leq1 (Lmax

2)

District of Sound Source District of Receiving Property

Residential Commercial Industrial

Residential 55 (70) 57 (72) 60 (75)

Commercial 57 (72) 60 (75) 65 (80)

Industrial 60 (75) 65 (80) 70 (85)

1. Measurement time is 1-minute minimum for a constant sound source, 1-hour for a non-continuous sound source. 2. During measurement intervals, Lmax may exceed Leq limits by no more than 15 dBA. Source: SMC 25.08.410 Exterior Sound Level Limits

Modifications to the exterior sound level limits set forth in Table 2 above are outlined in SMC 25.08.420. These modifications are for certain times of the day, classification of receiving properties, and the type of sound generated. These modifications to the exterior sound level limits include the following reductions:

• 10 dBA during the nighttime hours between the hours of 10:00 PM and 7:00 AM during weekdays and 10:00 PM and 9:00 AM on weekends and legal holidays when the receiving property is within a Residential district.

• 5 dBA for sources that carry a pure tone component.

• 5 dBA for impulsive sources not measured with an impulse sound level meter.

These modifications are cumulative and independent of one another. Therefore, the permissible nighttime exterior sound level in a Residential district for an impulsive, tonal source would be 20 dBA less than the exterior sound levels described in Table 2 above.

The area surrounding the Transfer Station is a mix of Residential (SF 5000) to the North and East, Commercial (C2) to the North, East and Southwest, and Industrial Commercial (IC-45) to the West and South. The Site is zoned Industrial Buffer, Industrial Commercial as well as Commercial, however the community agreement requires that for the evaluation of compliance with Noise Code, the entire site is considered a Commercial zone. The permissible daytime sound level limits for the Transfer Station at receiving property lines are summarized in Table 3 below.

Table 3. Transfer Station Sound Level Limits, Leq (Lmax)

Time Period Residential Commercial Industrial

Daytime 57 (72) 60 (75) 65 (80)

Nighttime 47 (62) 60 (75) 65 (80)



SOUND LEVEL MEASUREMENTS

Staffed sound level monitoring took place between 8:00 AM to 9:00 AM on Saturday July 6, 2019 and from 8:00 AM and 5:30 PM on Wednesday July 10, 2019. The measurements on July 6, 2019 were conducted to assess compliance with nighttime SMC sound level limits while the North Transfer Station operates between 8:00 AM and 9:00 AM on weekends, when nighttime sound level limits apply. Measurements on July 10, 2019 were made for the duration of the North Transfer Station’s operating hours and coincided with the facility’s peak operating times based on information provided by Seattle Public Utilities (SPU).

During both measurement periods, sound levels were monitored concurrently near two residential properties north and east of the Transfer Station. The wind speed was calm on July 6, 2019 and temperatures ranged between 58- and 60-degrees Fahrenheit. On July 10, 2019, winds averaged 1.8 miles per hour from the southwest and temperatures ranged between 61- and 67-degrees Fahrenheit. No precipitation was recorded on July 6, 2019. On July 10, 2010 0.3 inches of precipitation was measured.

Monitoring staff were stationed near the sound level meters to document specific on-site noise events. Measurements were conducted in general accordance with the most recent version of ASTM E1503.

Measurement Equipment

Sound level measurements were conducted using ANSI Type 1 instrumentation calibrated by a certified laboratory within one year of the measurement date. Equipment used during the measurements are identified in the Table below.

Table 4. Measurement Equipment

Make and Model Description Serial

Svantek 971 Sound level analyzer 51818

Svantek SV18 Preamplifier 94561

Aco Pacific 7052E Microphone 62522

LD CAL200 Acoustic Calibrator 9512

Svantek SV200 Sound level analyzer 39777

MK250 Microphone 10978

Larson Davis CAL200 Acoustic Calibrator 9512

Field calibrations of monitoring equipment were performed immediately before the measurements and verified after the measurements were completed. Audio recordings were made at both monitoring locations to allow for sound source identification after the measurements were completed. One-second and hourly average (Leq) and maximum (Lmax) sound levels were collected during the monitoring.



Measurement Locations

Sound levels were measured at two residential properties near the Transfer Station. Microphones were positioned as close to residential property lines as feasible at approximately 10 feet above grade. A figure showing the measurement locations as well as the address closest to the monitoring locations are provided below.

• Location 1: 3512 Ashworth Avenue North (approximate)

• Location 2: 3420 Woodlawn Avenue North

Figure 1. Measurement Locations

Photos of the sound monitoring equipment at the two monitoring locations are provided in Photos 1 and 2 below.

Photo 1. Equipment at Location 1

Photo 2. Equipment at Location 2



RESULTS

After the measurements were completed, data were reviewed to identify noise events associated with SMC exceedances. Due to the high number of off-site sound sources at the monitoring locations, average sound levels (Leq) from the Transfer Station were not able to be determined, therefore the analysis was restricted to maximum sound levels (hourly Lmax) only. Off-site sound sources included vehicle traffic, car horns and doors, aircraft, pedestrians, and wildlife. Figures illustrating the measured Lmax sound levels and identifying all events above the SMC Lmax sound level limit are provided in the Appendix.

Results of the analysis show that none of the Lmax exceedances were caused by the Transfer Station.

Seattle Municipal Code Exceedances

During the measurements, a combined total of 1,177 seconds of data were above either the SMC daytime or nighttime Lmax sound level limits, all resulted from off-site sound sources including vehicle traffic, car horns and doors, aircraft, pedestrians, and wildlife. These off-site sound sources are summarized in Table 5 below and are presented graphically in the Appendix.

Table 5. Number of Seconds Off-Site Sound Sources Exceeded SMC Lmax Limits

Event July 6, 2019 July 10, 2019 Total

Events Location 1 Location 2 Location 1 Location 2

Vehicle 204 47 337 76 664

Car Horn 0 0 12 11 23

Plane 66 81 160 135 442

Pedestrian 0 2 6 5 13

NTS 0 0 0 0 0

Car door 6 0 4 3 13

Plane & Vehicle 2 5 5 0 12

Animals &irds 0 3 5 2 10

CONCLUSION

All operations at the North Transfer Station complied with daytime and nighttime Seattle Municipal Code Lmax sound level limits during the measurement periods.

Respectfully submitted;

Ellie Myers Justin Morgan, INCE



APPENDIX

Location 1 – July 10, 2019, Lmax Sound Levels


















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Greenbusch Memorandum Template